Key head



' limited cross-section that is possible due Patented June 6, 1944 UNITED s'rATEsrATl-:N'r OFFICE any nnen Hans Martin and Walter Franz, Erfurt, Germany; vested in the Alien Property Custodian Application October 22, 1940, Serial No. 362,296

Germany October 21, 1939 1 claim. ,(Cl. 1s-s9) This form of construction, especially the characteristic keyl head form, in comparison with the usual fiat typewriter machine key heads, makes special methods of preparation necessary in order to be able to make them economically.

It is, moreover, diillcult and time-consuming if the key shank hole and a passage continuing from this to the key head surface are used for .spraying in the diierently colored character composition, since the residue of the character material remains in the key shaft hole and must be removed therefrom with considerable dimculty. supplying of the character-forming material could be distributed only on the circumference of the key shank hole, which involves certain drawbacks. Even the arrangement already known in typewriter machine heads with passages which pass through the body of the head, outside the key shank hole, up to the bottom of the head cannot be used directly in the present type of head since in it comparatively long injection passages or dies corresponding to the same are required in the casting mold, which would have only slight durability because of the to space requirements.

These difficulties are eliminated by the present invention in that the injection passages and the key shankhoie are combined into a single continuous passage, for instance. cross-shape or T-shape in cross-section. In this way, the die for forming these holes is provided with a simple continuous reinforcement.

In the drawing, an illustrative example ot the invention is shown in a number oi' views in which: v

y Fig. `1 shows a key head embodying the in'- vention viewed from above;

Figs. 2 and 3 are lateral sections o! the same on lines 2-2 and 3-3, respectively, of Fig. 1; and

Fig. 4 is a perspective view in Partial section of a die for molding the passages.

'I'he key head shown by way ot example in Fig. 1 is one of themanlpulating keys or a calbOdY,

In like manner, the passages for thel culating machine that have a diierent shape from the other number keys. The useofthe invention, however. is not limited to this shape of head, it being applicable just as well to the number keys or other shaped parts to be provided with characters.

The cuadrangular key head lbody I exhibits an inclined surface la above, while below it passes into an abruptly constricted sleeve Ib. In the surface la, the character 2 to be made of a material oi another color is embedded (Fig, l), so that the surface of the character and that ofthe key body are located in one plane. A character channel vil cut out ofthe key head surface for the purpose (Figs. 2 and 3) has wallsl substantially perpendicular to the surface oi the head surface and a iiat channel bottom of the usual depth. Outlet openings 4a, 4b of an in- .iection passage 4 that is led up from the .bottom oi' the head body intercept the channel at a number of places., In the same direction as the injection passage 4 and standing at right angles to the same in the lengthwise direction is the usual opening 5 forthe reception of a key shank or key lever at the bottom of the head, which is closed at the top by an inclined end wall at a suitable distance from the key-head surface. The injection passage 4, on thecontrary, passes directly into the character channel 3, forming the above-mentioned discharge openings 4a, 4b, which are given dimensions such that in all cases a part of the body of the key-head more or less enclosed lby the line trace of the character remains in connection with the rest of the keyhead body.

The die for forming the passages presents a cruciform cross-section with the laterally project'- ing parts 6, 1, as seen in Fig. 4 and as shown in Dosition in the passages in Figs. 2 and 3. Of these parts, the part 6 intended to form the key shank hole is provided with sharply angular outer edges, while the die part 1 for forming the injection passage has rounded off edges and is constricted in cross-section at the places of attachment to the rest of the die form, s o as to prevent any possible escape ofthe contents of the passage toward the inside of the head. 'I'he top surface of' the stamp is cut back to conform to the above-describedshape and length of the injection passage 4 and the shank opening 5.

The manufacture of this type of head is accomplished just as with typewriter machine key heads 'by simultaneous molding of the outer shape and the inner passages of the key h ead the die reinforced by its constructional form permitting rapid penetration in the still plastic head material. Because of `its ribbed form, there is no danger that the die will bend or break oil.' during ordinary molding or pressing operations. The character material subsequently is sprayed, in the most simple way. into the finished key head from the bottom openings of t the injection passages.

We claim: A method of forming a key head comprising a body portion of plastic material and a character channel in the upper surface of the body portion nlled with a diilerently colored material. which comprises molding said body portion by pressing plastic material in a mold shaped to form the exterior surface of said body portion and said character channel with a die comprising two longitudinal portions extending laterally at right angles, one of said die portions penetrating into communication with said Vcharacter channel, thereafter inserting a core member corresponding in cross-section to the shank to be inserted il said key head into the space formed by the other of said die portions and injecting diilerently colored material into said character channel through the remaining space formed by the first-mentioned portion oi.' said die.

HANS MARTIN. WALTER FRANZ. 

